1. Field of the Invention
This present invention relates to a braking device and more particularly to a braking device for thermo-plastic friction welding machines. The present invention also relates to an integral braking means for braking a live tool or spindle.
2. Background of the Invention
In the art of joining thermo-plastic articles by friction welding, a device may be used which spinwelds thermo-plastic axially mating sections. The sections are driven in rotation relative to each other and then axially abutted in mating relationship. In a device such as that disclosed in U.S. Pat. No. Re. 29,448, one of the two mating sections is chucked to an inertial member which is brought up to speed by a rotary drive. The rotary drive is uncoupled as the sections are moved into axial abutment and the braking of the inertial member by the axial abutment of the sections is transformed into frictional heat which welds the thermo-plastic seams to each other.
The apparatus described above may typically be a part of a larger apparatus such as that disclosed in U.S. Pat. No. 3,800,376 for performing a plurality of successive operations with individual container sections.
The processing operations may typically include the dispensing of container sections and the assembly, filling and sealing of the containers. On a single platform, a plurality of spaced processing units may be rotatably mounted. Each unit will typically include a plurality of circumferentially spaced carrier stations for moving container sections or containers about the unit's axis of rotation. A plurality of spaced star wheel transfer units may then be disposed intermediate and adjacent to the processing units. The star wheels receive container sections or containers from and deliver them to the processing units at transfer zones defined generally tangentially of each of the processing units and an adjacently disposed star wheel unit. A transfer unit may be rotatably mounted on the platform and may include a plurality of circumferentially spaced carrier stations for moving the container sections or containers about the axis of rotation. The circumferential spacing of the carrier station on the transfer and processing units will typically be substantially the same throughout; and the transfer and processing units are geared together for simultaneous rotation, with the carrier stations of each of the processing units and an adjacently disposed transfer unit rotating in opposite angular directions. The initial processing units will typically have dispensers for supplying individual container sections to an adjacent transfer unit.
In addition, the invention may be useful with a friction welding machine for joining thermo-plastic container top and bottom parts which are moved continuously along a production line as disclosed in U.S. Pat. No. 3,759,770. Star wheel loading and unloading members incorporating suction pads for gripping the parts as they move to the holders where flutes, in at least some of the holders, communicate the suction chambers in the holders with a vacuum source, and also hold the parts during the friction welding operation may be used.
Alternatively, the invention may be useful in connection with a device such as that disclosed in U.S. Pat. No. 3,720,836 wherein a pedestal assembly for accurately receiving and positively capturing a lower thermo-plastic container half when it is being transferred into and rotated by a spin welding apparatus is disclosed. The spin welding apparatus frictionally joins the lower container half to an upper container half to form a unitary container. The lower container half is received by the pedestal assembly from a rotating star wheel transfer device which slides the lower container half onto a stage portion of the assembly. The pedestal assembly having the container half thereon is then rotated in an opposite direction from that of the star wheel transfer device. The pedestal assembly including the stage portion has a dome-shaped upper surface which cooperates with a complementary recessed bottom of the lower container half. Vacuum means are applied through a central opening in the pedestal assembly for aiding in the positive capture of the lower container half.
Other devices where the present invention may find applicability are disclosed in U.S. Pat. No. 3,216,874 to G. W. Brown; U.S. Pat. No. 3,220,908 to G. W. Brown et al; U.S. Pat. No. 3,316,135 to G. W. Brown et al; U.S. Pat. No. 3,499,068 to G. W. Brown; U.S. Pat. No. 3,607,581 to G. A. Adams; U.S. Pat. No. 3,669,809 to G. W. Brown; U.S. Pat. No. 3,701,708 to G. W. Brown et al; U.S. Pat. No. 3,708,376 to R. J. Mistarz et al; U.S. Pat. No. 3,726,748 to R. J. Mistarz et al; U.S. Pat. No. 3,726,749 to R. J. Mistarz et al; U.S. Pat. No. 3,744,212 to R. J. Mistarz et al and U.S. Pat. No. 3,847,014 to R. J. Mistarz. It will be appreciated by the artisan that the control system of the present invention and the method by which it operates can be adapted to other devices as well.
In general, during the spinwelding process, welds are produced by the storage of kinetic energy in the driving tool. When the two functional surfaces to be welded are brought into intimate contact, the kinetic energy is dissipated in the form of heat, thus resulting in fusion or welding of the surfaces brought together.
For purposes of the description which follows, a defective weld is defined as a failure to create a bond of adequate strength, usually due to a failure of either a loss of one of the surfaces to be welded through, for instance, a missing component or an inproper fit; or a mechanical failure of a driving tool or the driven position of one of the components to be welded.
When such a failure occurs and the tool or spindle continues to rotate, it becomes difficult to load another component onto the spindle. The moving spindle should be at rest when the component is loaded to prevent the likelihood of its flying off the rotating tool surface which may be rotating as fast as 2000 rpm. The prior art lacks a device for the integral braking of the spindle or tool on which the containers are carried in order to stop the rotation of the spindle so that the new container section may be loaded onto the spindle while it is at rest.